Because an axial flow fan is usually very directional, it is frequently associated with a rotating grille having blades or louvers thereon which divert the airflow issuing from the fan and thereby sweep a large area. However there is sometimes a need for the grille to be capable of being prevented from rotation, either with the blades arranged one above the other, or with them orientated at some angle so that the airflow from the fan can be deflected in a selected direction.